The present invention relates to testing of one or more of multiple radio frequency (RF) data packet signal transceiver devices under test (DUTs), and in particular, to testing one or more such DUTs in a wireless signal environment with reduced signal interference from the remaining DUTs.
Many of today's electronic devices use wireless signal technologies for both connectivity and communications purposes. Because wireless devices transmit and receive electromagnetic energy, and because two or more wireless devices have the potential of interfering with the operations of one another by virtue of their signal frequencies and power spectral densities, these devices and their wireless signal technologies must adhere to various wireless signal technology standard specifications.
When designing such wireless devices, engineers take extra care to ensure that such devices will meet or exceed each of their included wireless signal technology prescribed standard-based specifications. Furthermore, when these devices are later being manufactured in quantity, they are tested to ensure that manufacturing defects will not cause improper operation, including their adherence to the included wireless signal technology standard-based specifications.
One common and widely used example of such devices is mobile, or cellular, telephone system that complies with the Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) standard, used for voice and data communications (e.g., sending and receiving of text messages, Internet browsing, etc.). Such devices are produced in large quantities and must be individually tested during manufacturing as well as after the actual manufacturing process prior to final shipment and sale. As part of such testing, it is highly desirable and advantageous to test such LTE devices in such a manner as to simulate behavior during normal operations, i.e., by operating multiple LTE devices simultaneously among themselves and one or more network access points (e.g., often referred to as a base station or eNodeB). Under such conditions, there will often be several LTE devices (e.g., often referred to as user equipment, or UE) operating. Under normal circumstances, multiple devices are in connected state, i.e., in active communication with the access point, while multiple other devices are in an idle state, i.e., not currently in active communication with the access point. Additionally, there are periodic transmissions from the idle, or non-connected, devices seeking to initiate communications with the access point. Such transmissions may occur randomly due to attempts by the device users to initiate communications via the access point, or for purposes of various forms of data updates between the device and network. (The LTE standard defines such interactions between devices and access points as parts of random access channel (RACH) interactions and specifies signal parameters related to such interactions.)
When multiple LTE devices are being tested concurrently, the test system must simulate behaviors consistent with performance under the applicable standards of the access point as it controls interactions with and responses to the devices. For example, in the course of such testing, the test system may instruct a device among a group of connected devices to transmit for the purpose of measuring one or more particular signal or data characteristics. However, if one or more devices among the idle devices simultaneously initiate a RACH transmission, such transmission can interfere with such measurements of signal characteristics.
No inherent mechanisms exist under the LTE standard for preventing or mitigating such instances of interference among active, or connected, devices and inactive, or idle, devices. While such potential for signal interference among such devices can be limited by limiting the number of devices being tested concurrently, this results in longer test times and reduced test efficiencies.